I think several non-U.S. carriers will let you ride on the jumpseat if the plane is full but you have to buy a ticket. Years ago I rode jumpseat on a LH A320 intra-Europe. The plane was full so I was glad to get on but I had to buy some discounted ticket.
Originally Posted by
Freehills
Eh, selling buddy passes/ companion status has been/ is common in Western airlines as well.
As with any good deal from the airlines, some colleagues will abuse it and mess it up for everyone. 
There have been scams with the jumpseat with American carriers where the company issues a positive space ticket on another carrier for deadhead on duty and a pilot gets a free jumpseat instead. They then try to refund the ticket to themselves or rebook it for personal use. Then, when they get caught, the union spends thousands of dollars on lawyers to keep the perp from getting fired.
Most U.S. airlines now have reciprocal jumpseat agreements and some folks will commute for years on other carriers to get to their domicile for work. I've had war bride colleagues that commuted from Asia and the UK to pick up their trips.
On U.S. carriers I'm not aware of any charge for the jumpseat, however, internationally you sometimes run into departure taxes that must be paid in local currency at a counter on the other side of security a long way from the gate.